Polyvinyl chloride formulations

ABSTRACT

An extrudable polyvinyl chloride composition comprising from 80 to 99.9 percent by weight polyvinyl chloride for use in extruding a first part and a second part, wherein a fusion joint between the first extruded part and the second extruded part is formed by: A) composition at least a portion of a first terminal edge of the first extruded part and a first terminal edge of the second extruded part; B) engaging the melted terminal edges; and C) maintaining pressure between the engaged terminal edges to create a fused joint having a strength that is at least 50% of the tensile strength of the extruded part as measured by ASTM D638-2a. The extruded parts can be pipe sections.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/598,451, filed Nov. 13, 2006, now U.S. Pat. No. 7,842,769, which is acontinuation of U.S. patent application Ser. No. 10/865,504, filed Jun.10, 2004, now abandoned, which claims priority from U.S. ProvisionalPatent Application No. 60/478,598, filed Jun. 13, 2003, each of whichare incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a polymer, and in particular to aformulation of polyvinyl chloride for use in repairing or reliningpipelines, such as for delivering water or gas under pressure, forgravity drain applications such as sanitary or storm sewer systems, orfor utility conduit applications.

2. Description of Related Art

Conduit systems are used extensively throughout the world in order totransfer or convey material, such as water and other fluids, fromlocation to location for distribution throughout the system. Forexample, extensive conduit systems are used to distribute water to bothresidences and businesses for use and further processes. Typically, suchconduit or piping systems are located underground, as aboveground pipingwould be both unsightly and intrusive.

Typical water conduit systems transport material through pipe, e.g.,cast iron, ductile iron, reinforced concrete, asbestos-cement, etc.,buried underground with the branches extending in various directions inorder to reach the end user. Normally, with age or for some otherreason, the present piping fails and begins to leak, thereby reducingline pressure and unnecessarily allowing water to leak into the areasurrounding the piping. Such leaks not only affect the system, butincrease the processing costs of the supplier which, in turn, increasesthe end user costs. Therefore, these leaks must be quickly repaired andpreventative measures taken to ensure that further leakage is prevented.

Due to the underground positioning of the conduit system, repairing aleaking pipe is particularly labor intensive and time consuming.Trenches must be dug along the pipeline to locate the leak andeffectively repair it prior to putting the pipe back in service. Variouslining systems have been developed according to the prior art in anattempt to seal a leaking pipe or a pipe that has fallen into disrepair,whether to repair a present crack or to preventatively ensure againstfuture cracks or breaks.

In addition, when a smaller diameter pipe is pulled through a largerdiameter pipe, the joints formed between sections of pipe must besufficiently strong to withstand the forces associated with pulling thepipe. In other words, the joints must not break or lose their integrity.

In another example, a method of pipe installation has been developed, asdisclosed in U.S. Pat. No. 5,794,662 to St. Onge et al., specificallydirected to pressurized pipeline applications. The St. Onge patent isdirected to a method of relining sewer lines, water lines or gas lines,and uses a segmented liner of reduced size relative to the pipe beingrelined. However, as opposed to merely leaving the small diameter linerconduit within the large diameter outer conduit, the method of the St.Onge patent uses heat and/or pressure to mold the reduced size pipe tothe shape of the pipe being relined. In particular, the inner or linerconduit is a thermoplastic pipe, typically a polyvinyl chloride (PVC)pipe that, when exposed to heat or pressure, expands and molds againstthe inside of an existing conduit to effect the relining of it. Thisprocess allows for both the lining of the entire length of pipe or onlya portion of it that is damaged, which is typically referred to as “spotrepair.”

According to the St. Onge patent, once the length of the liner conduitis inserted into the existing or host conduit, the liner conduit isplugged at either end and exposed to steam under pressure to heat theliner conduit along its length and apply pressure, which urges it toexpand and contact the interior walls of the surrounding host conduit.Once the liner conduit has fully expanded to conform to the interiorsurface of the existing conduit, it is cooled and the plugs are removed.The resulting expanded liner conduit conforms to the walls of the hostconduit, thereby preventing any further leakage. Also, the method of theSt. Onge patent requires only trenches to be dug at either end of thesection to be repaired.

While the St. Onge patent represents an advance in the art of reliningor repairing underground conduit systems, there is room in the art foradditional improvements and advancements. One such area is in the typeof material used to form the liner conduit. A commonly used material formanufacturing conduit and pipe as mentioned above is polyvinyl chloride.

It is known to use extruded PVC pipe in conduit systems. Certainthermoplastic pipe, in particular PVC pipe, when heated and exposed topressure, can be expanded and molded against the inside of an existingor host pipe to effect relining thereof. Furthermore, it is possible tohave joints between pipe segments and subject the joined pipes to therequired heat and pressure with the resultant combination expanded andmolded against the host pipe to be relined with the integrity of thejoints being maintained. The pipe segments can be of traditionalsections, easily installed due to the reduced diameter and merelyappropriately sized once properly located.

Published standards for PVC pipe used in water lines are available (seefor example PPI PVC Range Composition, Listing of Qualified IngredientsTR-2/2004, Plastics Pipe Institute, Washington, D.C., 2004) and providelists of acceptable additives and ranges therefor that can be used.However, known combinations of additives do not work in the conduitexpansion process. In particular, fusion joints formed between pipesections either break on expansion or burst when exposed to in-linewater pressure and/or are too weak to withstand the pull force appliedas the PVC pipe is pulled through an existing conduit. Moreparticularly, existing extruded PVC water pipes do not fuse to formfusion joints that are anywhere near as strong as the extruded pipeitself.

One example of a PVC formulation includes, in parts per hundred parts ofresin: 100 PVC resin, 0.3-1.0 heat stabilizer, 0.4-1.5 calcium stearate,0.6-1.5 paraffin wax, 0-0.3 polyethylene wax, 0.5-3.0 titanium dioxide,0-5.0 calcium carbonate, 0-2.0 process aid and 0-5.0 colorant as recitedin PPI PVC Range of Composition, Listing of Qualified Ingredients,published by the Plastics Pipe Institute. However, prior art PVCformulations that fall within the ranges set forth in this PPI standarddo not appear to achieve the desired expansion or fusion joint strengthproperties required for PVC liner conduit utilized in relining and/orconduit expansion processes.

Thus, a need remains for the formulation of polyvinyl chloride that hasexcellent elastomeric and expandability properties and/or form fusionjoints approaching the strength of the extruded PVC pipe itself, andthat can be used for relining water mains, fire protection lines,gravity drain systems and utility conduit applications.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide aformulation of polyvinyl chloride to overcome the deficiencies of theprior art. It is another object of the present invention to provide aformulation of polyvinyl chloride that has improved elastomeric andexpandability characteristics and properties. It is a still furtherobject of the present invention to provide a formulation of polyvinylchloride appropriate to form fusion joints that approach the strength ofthe extruded PVC pipe itself. It is yet another object of the presentinvention to provide a formulation of polyvinyl chloride that isparticularly useful in connection with relining water mains, fireprotection lines, gravity drain systems and utility conduitapplications.

The present invention is directed to an extrudable polyvinyl chloridecomposition comprising from 80 to 99.9 percent by weight polyvinylchloride for use in extruding a first part and a second part, wherein afusion joint between the first extruded part and the second extrudedpart is formed by:

A) melting at or above a melting temperature of the polyvinyl chloridecomposition at least a portion of a first terminal edge of the firstextruded part and a first terminal edge of the second extruded part;

B) engaging the melted terminal edges; and

C) maintaining pressure between the engaged terminal edges to create afused joint having a strength that is at least 50% of the tensilestrength of the extruded part as measured by ASTM D638-2a.

The present invention is also directed to an extruded part that includesthe above-described polyvinyl chloride composition to a joint thatincludes these resultant characteristics and, in particular, to anextruded part that is a section of pipe.

The present invention, both as to its construction and its method ofoperation, together with the additional objects and advantages thereof,will best be understood from the following description of exemplaryembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an apparatus and system for a fusionprocess for conduit according to U.S. Pat. No. 6,982,051; and

FIG. 2 is a side sectional view of a fused joint area resulting from thefusion process for conduit according to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Other than in the operating examples or where otherwise indicated, allnumbers or expressions referring to quantities of ingredients, reactionconditions, etc., used in the specification and claims are to beunderstood as modified in all instances by the term “about.” Variousnumerical ranges are disclosed in this patent application. Because theseranges are continuous, they include every value between the minimum andmaximum values. Unless expressly indicated otherwise, the variousnumerical ranges specified in this application are approximations.

The present invention provides an extrudable polyvinyl chloridecomposition capable of forming a fusion joint between a first extrudedpart and a second extruded part, where the strength of the fusion jointis at least 50%, in some cases at least 60%, in other cases at least70%, in some instances at least 80%, in other instances at least 90% andin some instances at least 95% of the tensile strength of the extrudedpart as measured by ASTM D638-2a. In some embodiments of the invention,the fusion joint can be as strong as or stronger than the extruded part,for example the fusion joint can be 100% or more of the tensile strengthof the extruded part. The strength required can vary depending on theintended use of the extruded part. As a non-limiting example, theextruded part can be a section of pipe, and the fusion bond strengthmust be sufficiently high so that the pipe sections do not pull apartwhen the pipe is pulled through an existing conduit, or installed aspart of other rehabilitative or other pipe installation methods.Further, the fusion joint must be sufficiently strong to maintain itsintegrity during expansion operations, as well as withstanding thepressure and wear and tear involved in daily service.

Typically, the fusion joint is formed by melting at or above a meltingtemperature of the polyvinyl chloride composition at least a portion ofa first terminal edge of the first extruded part and a first terminaledge of the second extruded part; engaging the melted terminal edges;and maintaining pressure between the engaged terminal edges to create afused joint. The method of forming the fusion joint is disclosed inco-pending U.S. Application Ser. No. 10/788,921 filed Feb. 26, 2004,which is herein incorporated by reference.

The present extrudable polyvinyl chloride composition can contain atleast 80%, in some cases at least 85%, in other cases at least 90% andin some situations at least 95% polyvinyl chloride based on the weightof the composition. Also, the extrudable polyvinyl chloride compositioncan contain up to 99.95%, in some cases 99.9%, in other cases up to99.5% and in some instances up to 99% polyvinyl chloride by weight. Theamount of polyvinyl chloride in the extrudable polyvinyl chloridecomposition will depend on the amount of other additives included in thecomposition. The amount of polyvinyl chloride can be any value or rangebetween any values recited above.

In an embodiment of the invention, the polyvinyl chloride compositionwill include virgin polyvinyl chloride and in particular embodiments,exclusively virgin polyvinyl chloride. As used herein, the term “virginpolyvinyl chloride” refers to polyvinyl chloride that has not beenpreviously molded, extruded or compounded to form an article.

In an embodiment of the invention, the polyvinyl chloride has a numberaverage molecular weight (Mn) of at least 20,000, in some cases at least30,000, and in other cases at least 40,000. Also, the polyvinyl chloridehas an Mn of up to 100,000, in some cases up to 95,000, and in othercases up to 90,000. The molecular weight of the polyvinyl chloride canbe determined by gel permeation chromatography using polystyrenestandards. The Mn of the polyvinyl chloride can be any value or rangebetween any of the values recited above.

When non-virgin polyvinyl chloride is used, it can often behave as afiller material, as described below, and not be homogeneously co-mingledwith the virgin polyvinyl chloride. In an embodiment of the invention,when non-virgin polyvinyl chloride is used, it is melt blended withvirgin polyvinyl chloride in order to minimize the above-described“filler effect.”

A number of additives can be included in the present extrudablepolyvinyl chloride composition so long as the composition is able toform fusion bonds as described above and/or possess the propertiesrequired for successful expansion operations. Non-limiting examples ofmaterials that can be included in the extrudable polyvinyl chloridecomposition include other resins, heat stabilizers, lubricants, fillers,colorants, compounds capable of providing protection against ultraviolet(UV) radiation, processing aids, as well as other ingredients known inthe art.

The present polyvinyl chloride composition can be formed by meltblending the various components, or by dry blending followed by meltingthe various components using methods known in the art. The compositionis then extruded using known methods to form an article or part, in someembodiments, a section of pipe.

As used herein, the term “heat stabilizer” refers to materials thatprevent, inhibit, or slow the degradation of PVC at the elevatedtemperatures required in thermoplastic processing. As a non-limitingexample, heat stabilizers inhibit dehydrochlorination, auto-oxidation,mechano-chemical chain scission, crosslinking and/or condensationreactions of the PVC. Any suitable material that acts as a heatstabilizer and either aids in or does not substantially interfere withthe fusion bonding and/or expansion properties of the PVC can be used inthe invention. Non-limiting examples of heat stabilizers that can beused in the invention include the THERMOLITE® heat stabilizers availablefrom ATOFINA Chemicals, Inc. Philadelphia, Pa.; the MARK™ heatstabilizer products available from Crompton Corporation, New York, N.Y.;the ADVERA® heat stabilizer products available from PQ Corporation,Valley Forge, Pa.; the ADVASTAB® heat stabilizer products available fromRohm & Haas Company, Philadelphia, Pa.; and the ADVAFLEX® heatstabilizer products available from Morton International, Inc., Chicago,Ill.

The amount of heat stabilizer, when used, can be at least 0.001, in somecases at least 0.01, in other cases at least 0.1 percent, and in somesituations at least 0.2 percent by weight based on the composition.Also, the amount of heat stabilizer, when used, can be up to 1.5, insome cases up to 1.25, in other cases up to 1, and in some cases up to0.9 percent by weight based on the composition. The amount of heatstabilizer used will be an amount sufficient to inhibit PVC degradationwhile allowing the composition to form fusion bonds as described aboveand/or possess the properties required for successful expansionoperations. The amount of heat stabilizer used in the composition can beany value or range between any values recited above.

Any suitable lubricant can be used in the present composition. As usedherein, the term “lubricant” refers to materials added to PVC to improveprocessing, for example extruding, such that the lubricant(s) preventthe PVC from sticking, for example, to metal walls of extruder barrels,calenders, mills, etc., providing smooth passage of the melt and/or toreduce the melt viscosity and prevent overheating of the PVC. Asnon-limiting examples, suitable lubricants include divalent metal saltsof aliphatic carboxylic acids and waxes.

In an embodiment of the invention, the lubricant includes one or more C₆to C₃₂ linear, branched or cyclic alkyl, alkenyl, aryl, aralkyl oralkaryl carboxylic acids and/or their corresponding C₁-C₄ alkyl estersor metal salts thereof. The above-described carboxylic acids can bepresent in the polyvinyl chloride composition at a level of at least0.1, in some cases 0.25 and in other cases at least 0.5 percent byweight of the composition. Also, the carboxylic acids can be present atup to 5, in some cases up to 4, in other cases up to 3, and in othercases up to 2 percent by weight of the composition. In a particularembodiment of the invention, the carboxylic acid is present as adivalent metal salt. In a more particular embodiment of the invention,the divalent metal salts of carboxylic acids include calcium stearate.The amount of carboxylic acid used in the composition can be any valueor range between any values recited above.

When waxes are included in the present composition as lubricants, anysuitable wax can be used. Non-limiting examples of suitable waxes thatcan be used in the composition include hydrocarbon waxes, such asparaffinic waxes, and polyolefin waxes, such as polyethylene waxes. Moreparticular non-limiting examples of waxes that can be used in theinvention include the SUNOLITE® and HYDROBRITE® lubricants availablefrom Crompton Corporation, the DOVERLUBE® lubricants available fromDover Chemical Corporation, the LOOBWAX™, RHEOLUBE™ and A-C® lubricantsavailable from Honeywell, Inc., the INTERFLO® lubricants available fromthe International Group, Inc., the LUX® lubricants available from LuxInternational Inc., the MARCUS™ lubricants available from Marcus Oil &Chemical Inc., the MOORELUBE™ and PARAFLINT® lubricants available fromMoore & Munger Inc., the C WAX™ and RW™ lubricants available fromReagens USA, the LUWAX® lubricants available from BASF Corporation, andthe LUBOL® lubricants available from L&L Industrial Chemicals Inc.

When waxes are included as lubricants in the polyvinyl chloridecomposition, they are included at a level of at least 0.1, in some cases0.25, in other cases at least 0.5 and in some situations at least 1percent by weight of the composition. Also, the waxes can be included inthe composition at up to 5, in some cases up to 4.5, in other cases upto 4, in some situations up to 3 and in other situations up to 2 percentby weight of the composition. The amount of waxes used in thecomposition can be any value or range between any values recited above.In a particular embodiment of the invention, the waxes used in thecomposition include paraffin waxes and/or polyethylene waxes.

Regardless of the particular lubricant used, the amount of lubricantwill be an amount sufficient to provide desired lubrication propertieswhile allowing the composition to form fusion bonds as described aboveand/or possess the properties required for successful expansionoperations. In an embodiment of the invention, two or more lubricantsare combined, mixed, and then added to the PVC composition.

In an embodiment of the invention, one or more suitable fillers areincluded in the extrudable polyvinyl chloride composition. Suitablefillers include materials that are used to lower the cost of the PVCand/or to impart special properties such as hardness, abrasionresistance, and/or non-sticking, while not adversely affecting fusionjoint formation or expansion properties. Suitable fillers include, butare not limited to, inorganic materials such as calcium carbonate,barite, silica, silicate, carbon black, pigments, kaolin and/or chinaclay. In a particular embodiment of the invention, the fillers areselected from the group consisting of pigments, clays, calciumcarbonate, silica, carbon black and combinations thereof.

When fillers are included in the polyvinyl chloride composition, theyare included at a level of at least 0.1, in some cases 0.25, in othercases at least 0.5 and in some situations at least 1 percent by weightof the composition. Also, the fillers can be included in the compositionat up to 5, in some cases up to 4.5, in other cases up to 4, in somesituations up to 3 and in other situations up to 2 percent by weight ofthe composition. The filler is present in an amount sufficient toprovide desired properties while allowing the composition to form fusionbonds as described above and/or possess the properties required forsuccessful expansion operations. The amount of fillers used in thecomposition can be any value or range between any values recited above.

In a particular embodiment of the invention, the filler can have anysuitable shape, such as spherical, elliptical, or plate-like. The fillerparticles can have any suitable particle size that allows for providingdesired properties. The particle size can be at least 0.01, in somecases at least 0.1, in other cases at least 0.25 and in some situationsup to 0.5 μm. Also, the particle size of the fillers can be up to 3, insome cases up to 2 and in other situations up to 1 μm. The particle sizeof the filler is typically large enough to provide easy handling andlower cost but not so large as to cause weak points to form in the PVCcomposition that can adversely impact the strength of fusion bonds asdescribed above and/or the strength of the PVC composition afterexpansion operations. The particle size of the filler can be any valueor range between any values recited above.

In an embodiment of the invention, the particle size distribution istypically as close to one as is practical, and is typically less than 2.Particle size and particle size distribution can be determined usinglight scattering methods, such as with a MASTERSIZER® instrumentavailable from Malvern Instruments, Ltd.

Any suitable UV stabilizer, i.e., compounds capable of providingprotection against ultraviolet (UV) radiation, can be used in thepresent invention. Examples of suitable UV stabilizers include, but arenot limited to, hindered amine light stabilizers and UV absorbers suchas those available under the trade names TINUVIN® and CHIMASSORB® fromCiba Specialty Chemicals, as well as titanium dioxide.

In an embodiment of the invention, when titanium dioxide is used, it canhave any suitable particle size that allows for providing desiredproperties. The particle size can be at least 0.001, in some cases atleast 0.01, in other cases at least 0.1 and in some situations up to0.25 μm. Also, the particle size of the titanium dioxide can be up to 2,in some cases up to 1 and in other situations up to 0.75 μm. Theparticle size of the titanium dioxide is typically large enough toprovide easy handling and lower cost but not so large as to cause weakpoints to form in the PVC composition that can adversely impact thestrength of fusion bonds as described above and/or the strength of thePVC composition after expansion operations. The particle size of thetitanium dioxide can be any value or range between any values recitedabove.

In an embodiment of the invention, the particle size distribution of thetitanium dioxide is typically as close to one as is practical and istypically less than 2. Particle size and particle size distribution canbe determined using light scattering methods, such as with aMASTERSIZER® instrument available from Malvern Instruments, Ltd.

When compounds providing protection against UV radiation are included inthe polyvinyl chloride composition, they are included at a level of atleast 0.1, in some cases 0.25, in other cases at least 0.5 and in somesituations at least 1 percent by weight of the composition. Also, thecompounds providing protection against UV radiation can be included inthe composition at up to 5, in some cases up to 4.5, in other cases upto 4, in some situations up to 3 and in other situations up to 2 percentby weight of the composition. The compounds providing protection againstUV radiation are present in an amount sufficient to prevent PVCdegradation due to UV exposure prior to being places into service, whileallowing the composition to form fusion bonds as described above and/orpossess the properties required for successful expansion operations. Theamount of compounds providing protection against UV radiation used inthe composition can be any value or range between any values recitedabove.

Any suitable processing aid known in the art can be used in the presentinvention. Suitable processing aids are those that do not have anadverse affect on the fusion bond. Suitable processing aids include, butare not limited to copolymers including methacrylic esters, acrylicesters, acrylonitrile and/or styrene. The amount of processing aids,when used, can be at least 0.001, in some cases at least 0.01, in othercases at least 0.1 percent, and in some situations at least 0.2 percentby weight based on the composition. Also, the amount of processing aidscan be up to 2, in some situations up to 1.5, in some cases up to 1.25,in other cases up to 1, and in some instances up to 0.9 percent byweight based on the composition. The amount of processing aids used willbe an amount sufficient to provide efficient processing of the PVC whileallowing the composition to form fusion bonds as described above and/orpossess the properties required for successful expansion operations. Theamount of processing aids used in the composition can be any value orrange between any values recited above.

The present polyvinyl chloride composition typically has a meltingtemperature of at least 125, in some cases at least 150, in many casesat least 175° C., and in some situations at least at least 190° C.

As indicated above, the polyvinyl chloride composition of the inventionis used to form parts, in many cases sections of pipe, that can becombined through heat fusion. In heat fusion, portions of the PVC partsare heated above their melting point and fused together by applicationof force. The pressure causes flow of the melted materials, whichintermix such that when the fusion joint is cooled, the strength of thejoint approaches or even surpasses the strength of the PVC parts. In anembodiment of the invention, PVC pipe sections are joined by heat fusionusing a fusion machine.

In an embodiment of the invention, during heat fusion, the PVC is heatedto at least 125, in some cases at least 150, in other cases at least175, and in some situations at least 190° C. Also, the PVC can be heatedto up to 300, in some cases up to 250, in other cases up to 230, and insome situations up to 200° C. The PVC is heated to a temperature thatwill allow sufficient flow for the fusion joint to form but not so higha temperature that the PVC is degraded or excessive flow occurs. Theheat fusion temperature can be any value or range between any valuesrecited above.

During the heat fusion process, the interfacial pressure maintainedbetween the engaged terminal edges is at least 50 psi (344,750 Pa), andin some cases at least 75 psi (517,125 Pa) and can be up to 250 psi(1,723,750 Pa), in some situations up to 200 psi (1,379,000 Pa) or insome cases up to 150 psi (1,034,250 Pa). The heat fusion pressure is apressure that will allow sufficient flow for the fusion joint to formbut not so high that the material crumples or forms an overly thickseam. The heat fusion pressure can be any value or range between anyvalues recited above.

During the heat fusion process, the temperature and pressure are appliedfor at least 5 seconds, in some instances at least 15 seconds, in otherinstances at least 30 seconds, in many cases at least 1 minute and inother cases at least 2 minutes. Also the heat fusion process can beconducted for up to 30 minutes, in some cases 20 minutes, in other casesup to 15 minutes, and in some instances up to 10 minutes. The heatfusion process is conducted for a period of time required to form afusion joint with the characteristics described above. The heat fusionpressure can be conducted for any length of time or range between anylengths of time recited above. The heat fusion joint is allowed to coolover a period of time necessary for the fusion joint to properly formand develop its strength.

The present invention is also directed to extruded parts that containthe above-described polyvinyl chloride composition. As such, embodimentsof the invention are directed to an extruded part that includes two ormore extruded parts where at least one terminal edge of each part isfused together with at least one terminal edge of another part. In aparticular embodiment of the invention, the extruded parts are sectionsof pipe.

In an embodiment of the invention, the fused PVC pipe sections arepulled through an existing underground conduit. As such, the fused pipesections are inserted into the conduit and pulled through the conduitwith constant tension being applied. The heat fusion joint issufficiently strong that it does not break under the application of thistension.

More specifically, for sections of pipe where the terminal ends of atleast two sections of pipe have been fused together as described above,the strength of the fusion joint is at least 50%, in some cases at least60%, in other cases at least 70%, in some instances at least 80%, inother instances at least 90% and in some instances at least 95% of thetensile strength of the extruded pipe itself as measured by ASTMD638-2a. In some embodiments of the invention, the fusion joint can beas strong as or stronger than the extruded part. As a non-limitingexample, the strength of the fusion joint can be determined usingtensile testers known in the art such as the McSNAPPER™ instrumentavailable from McElroy Manufacturing Inc. as described in the “McElroyFusion Catalog Reference Guide” pages 33-1 and 33-2, McElroyManufacturing Inc., 2002.

The pipe sections according to the invention can have a diameter of atleast 0.5 inches (1.25 cm), in some instances at least 1 inch (2.54 cm),in other instances at least 2 inches (5.1 cm), in some situations atleast 3 inches (7.6 cm), in some cases at least 4 inches (10 cm), and inother cases at least 5 inches (12.7 cm). Also, pipe sections accordingto the invention can have a diameter of up to 60 inches (153 cm), insome cases up to 40 inches (101.6 cm) and in other cases up to 30 inches(76.2 cm). The diameter of the pipe sections according to the inventioncan be any value or range between any of the values recited above.

The pipe sections according to the invention have a wall thickness of atleast 0.05 inches (0.125 cm), in some cases at least 0.1 inches (0.25cm), and in other cases at least 0.25 inches (0.64 cm). Also, the pipesections according to the invention have a wall thickness of up to 3inches (7.6 cm), in some cases up to 2 inches (5 cm), in other cases upto 1 inch (2.5 cm) and in some situations up to 0.5 inches (1.25 cm).The wall thickness of the pipe sections can be any value or rangebetween any of the values recited above.

In an embodiment of the invention, after the pipe sections have beeninserted into an existing conduit, the pipe sections can be heated andpressure applied to expand the pipe sections to the inner diameter ofthe conduit. The temperature and pressure are high enough to effectexpansion while not substantially degrading the strength of the pipesections.

After heating, pressure is applied, which can be at least 50 psi(344,750 Pa), in some cases at least 60 psi (412,700 Pa), in other casesat least 75 psi (517,125 Pa) and in some situations at least 100 psi(689,500 Pa). Also, the pressure can be up to 200 psi (1,379,000 Pa), insome cases at least 175 psi (1,206,625 Pa) and in other cases at least150 psi (1,034,250 Pa). The expansion pressure can be any value or rangebetween any values recited above.

In the expansion operation, the diameter of the pipe is expanded atleast 1.05 times, in some instances at least 1.1 times, in some cases atleast 1.25 times and in other cases at least 1.5 times the original pipediameter. Also, the expanded pipe diameter can be up to 3 times, in somecases up to 2.5 times and in other cases up to 2 times the original pipediameter. The expanded diameter can be any value or can range betweenany of the values recited above.

In the expansion operation, the wall thickness of the pipe is reduced atleast 0.98, in some instances at least 0.95, in some cases at least 0.9and in other cases at least 0.85 times the original pipe wall thickness.Also, the expanded pipe wall thickness will be not less than 0.3, insome cases not less than 0.5 and in other cases not less than 0.65 timesthe original pipe wall thickness. The wall thickness of the expandedpipe can be any value or can range between any of the values recitedabove.

The pressure rating of the expanded pipe is at least 50%, in some casesat least 60%, in other cases at least 75%, in some situations at least85% of the pressure rating of the pre-expanded pipe and the hydrostaticdesign basis can be at least 100% and in some cases up to 175% or moreof the hydrostatic design basis of the pre-expanded pipe.

Particular embodiments of the invention are directed to an extrudablepolyvinyl chloride composition that contains from 80 to 99.9 percent byweight polyvinyl chloride. Pipe sections formed by extruding thepolyvinyl chloride composition, which are expanded such that theexpanded tube diameter is from 1.05 to 3 times the pre-expanded tubediameter, have a pressure rating and/or hydrostatic design basis of atleast 50% of the pressure rating of the pre-expanded pipe as measuredaccording to ASTM D2241, AWWA C900, and/or AWWA C905.

Embodiments of the invention provide a water pipe that includes pipesections as described above, that have been fused together by heatfusion and that include the above-described polyvinyl chloridecomposition. The water pipes can be positioned within an existingconduit or expanded, as described above within the conduit, inserted inhorizontal lines, drilling mounted, pipe bushing, guided boring, directboring and other applications.

Water pipes according to the invention have a burst strength of at least200 psi (1,379,000 Pa), in some instances at least 350 psi (2,413,250Pa), in other instances at least 500 psi (3,447,500 Pa), in some casesat least 750 psi (5,171,250 Pa) and in other cases at least 890 psi(6,136,550 Pa) as determined by ASTM D1785 in accordance with ASTM D1599(Procedure B).

In an embodiment of the invention, the PVC compositions and water pipescontaining such meet the requirement for use with potable water, such asthose set forth in PPI PVC Range Composition, Listing of QualifiedIngredients TR-2/2004, Plastics Pipe Institute, Washington, D.C., 2004,the relevant portions of which are herein incorporated by reference.

Embodiments of the invention also provide gravity drain pipes, forexample sanitary pipes, that includes pipe sections as described above,that have been fused together by heat fusion and that include the abovedescribed polyvinyl chloride composition. The gravity drain pipes can bepositioned within an existing conduit or expanded, as described abovewithin the conduit, inserted in horizontal directional drilling, pipebursting, guided boring, direct bury and other applications.

Embodiments of the invention also provide utility conduit, for exampleconduit through which electrical or fiber optic cables are run, thatincludes pipe sections as described above, that have been fused togetherby heat fusion and that include the above-described polyvinyl chloridecomposition. The utility conduit can be positioned within an existingconduit or expanded, as described above within the conduit, inserted inhorizontal directional drilling, pipe bursting, guided boring, directbury and other applications.

The present invention is more particularly described in the followingexamples, which are intended to be illustrative only, since numerousmodifications and variations therein will be apparent to those skilledin the art. Unless otherwise specified, all parts and percentages are byweight.

Example 1

This example is a polyvinyl chloride composition according to theinvention. The ingredients below were combined with 100% virgin PVCresin with no regrind and extruded to form 20 foot (6 m) PVC pipesections. (All ingredients are parts per hundred based on the PVCresin).

Ingredient Amount Lubricant combination of 2 pph calcium stearate,paraffin wax and polyethylene wax Titanium Dioxide 3 pph CalciumCarbonate 2 pph Processing Aid 1 pph (Rohm & Haas K120N) Blue Colorant0.2 pph   (Color Matrix) Heat Stabilizer 0.8 pph  

Example 2

Sections of pipe were extruded as in Example 1 having an outsidediameter of 6.6 inches and a wall thickness of 0.4 inches. Two sectionsof pipe were heat fused using a Model No. 28 hydraulic fusion machineavailable from McElroy Manufacturing, Inc. at 140 psi interfacialpressure, 204° C. for approximately two minutes and cooled under ambientconditions for about 15 minutes. Two samples were burst-tested accordingto ASTM D1785, section 6.3 in accordance with ASTM D1599 (Procedure B)at 23° C. after conditioning for 16 hours at 23° C. such that the firstsample consisted of only the pipe section (2A) and the second sample hadthe fusion bond (2B). The minimum acceptable burst pressure is 890 psi.The data are summarized below.

Sample 2A Sample 2B Burst Pressure 1210 psi 1190 psi Time-to Fail 95seconds 75 seconds

The heat fused extruded polyvinyl chloride pipe according to theinvention provides more than acceptable burst test performance. The pipedid not fail at the joint, but in a normal bursting mode.

Example 3

Pipe sections of 16-inch diameter were prepared as in Example 1. Thesections were heat fused as described in Example 2. Specimens wereremoved from the fused pipe with the fused section in the middle(samples in triplicate), as well as sections without the fusion joint.Izod impact testing was conducted on a set of samples according to ASTMD256-02. Tensile properties were evaluated according to ASTM D638-2a onsamples with and without the fusion joint at a speed of 0.2 inches perminute. Flexural properties were evaluated according to ASTM D790-03 onsamples with and without the fusion joint at a 16:1 span to depth ratio.The results are shown below:

Test Property Result Izod impact strength (no fusion joint) 0.59ft-lb/in Izod impact strength (with fusion joint) 0.41 ft-lb/in Tensilestrength at Yield (no fusion joint) 7020 psi Tensile strength at Yield(with fusion joint) 5775 psi Modulus of Elasticity (no fusion joint)391,900 psi Modulus of Elasticity (with fusion joint) 409,500 psiFlexural strength (no fusion joint) 11,395 psi Flexural strength (withfusion joint) 8,121 psi Flexural Modulus (no fusion joint) 429,000 psiFlexural Modulus (with fusion joint) 415,600 psi

The joint strength was about 82.5%. Thus, the examples show theexcellent strength of the fusion joints made according to the invention.

Example 4

Pipe sections of 4- and 6-inch diameter were prepared as in Example 1and heat fused as in Example 2 under the temperature/pressure conditionsin the table below. Coupons were cut from the pipe containing the fusedjoint in the middle, as well as coupons cut from the wall of the pipewithout any fusion joints. The coupons were evaluated using a McSNAPPER™instrument available from McElroy Manufacturing Inc. as described in the“McElroy Fusion Catalog Reference Guide” pages 33-1 and 33-2, McElroyManufacturing Inc., 2002. The results below show the stress at break forthe fusion joint sample and the corresponding percentage based on thenon-fusion sample.

Pipe Fusion Fusion Percentage of Diameter Pressure Temperature Stresscontrol sample 4″ 150 psi 204° C. 8905 psi 94% 4″ 150 psi 218° C. 9176psi 96% 4″ 130 psi 204° C. 9035 psi 95% 4″ 130 psi 218° C. 8957 psi 94%6″ 150 psi 204° C. 7641 psi 80% 6″ 150 psi 218° C. 8896 psi 93% 6″ 130psi 204° C. 7620 psi 80% 6″ 130 psi 218° C. 8999 psi 95%

Example 5

This example shows the expansion properties of the fused polyvinylchloride pipe sections according to the invention. Pipe sections of8-inch diameter were made as in Example 1 and heat fused as in Example2. The fused pipe sections were pulled through a 14-inch cast iron pipeand all fusion joints found to be intact after inspection. Water at 93°C. was circulated through the pipe for about 2 hours at a pressure ofabout 50 psi to bring the pipe to temperature. The circulation pumppressure was then increased to 225 to 240 psi and expansion and cooldown took about three hours, after which time the pressure was relievedand the water drained from the system. Inspection showed that the pipehad expanded to the diameter of the cast iron conduit and that allfusion joints were intact, showing no signs of fracture.

The experiment was repeated with pipes having different diameters, whichresulted in different wall thicknesses in the resulting expanded pipe.The hoop stress of pipe sections was measured according to ASTM D2290 atvarious wall thickness ratios (expanded wall thickness divided byoriginal wall thickness). The results are shown below.

Wall thickness ratio Hoop Stress (psi) Original, no expansion 8,000 1.18,750 1.2 9,700 1.3 10,000 1.6 11,900 1.8 13,000 1.9 14,500 2.1 15,000

The data shows the increase in hoop stress realized after expansion ofthe heat fused extruded PVC compositions of the present invention.

The present invention has been described with reference to specificdetails of particular embodiments thereof. It is not intended that suchdetails be regarded as limitations upon the scope of the inventionexcept insofar as and to the extent that they are included in theaccompanying claims.

1. A pipe composition consisting of: (a) 91 to 98 weight percentpolyvinyl chloride; (b) 0.5 to 1.0 weight percent heat stabilizer; (c)0.4 to 1.0 weight percent calcium stearate; (d) 0.9 to 1.6 weightpercent wax; (e) 1.0 to 2.0 weight percent titanium dioxide; (f) 0.001to 1.0 weight percent processing aid; (g) 0.1 to 1.9 weight percent ofcalcium carbonate; and (h) optionally, up to 2 weight percent ofpigment, based upon total weight of the pipe composition.
 2. The pipecomposition according to claim 1, wherein the pipe composition is afusion joint composition.
 3. The pipe composition according to claim 1,wherein the polyvinyl chloride is between 92 and 95 weight percent ofthe total weight of the pipe composition.
 4. The pipe compositionaccording to claim 1, wherein the polyvinyl chloride is virgin polyvinylchloride.
 5. The pipe composition according to claim 1, wherein the heatstabilizer is an organotin heat stabilizer.
 6. The pipe compositionaccording to claim 1, wherein the pipe composition comprises 0.5 to 0.8weight percent calcium stearate.
 7. The pipe composition according toclaim 1, wherein the wax is paraffin wax.
 8. The pipe compositionaccording to claim 1, wherein the wax is oxidized polyethylene wax. 9.The pipe composition according to claim 1, wherein the wax is paraffinwax and oxidized polyethylene wax.
 10. The pipe composition according toclaim 1, wherein the pipe composition comprises 0.95 to 1.4 weightpercent wax.
 11. The pipe composition according to claim 1, wherein thepipe composition comprises 0.9 to 1.0 weight percent of processing aid.12. The pipe composition according to claim 1, wherein the processingaid comprises methacrylic ester, acrylic ester, acrylonitrile, and/orstyrene.
 13. The pipe composition according to claim 1, wherein theprocessing aid comprises acrylic ester.
 14. A pipe composition accordingto claim 1, the pipe composition consisting of: (a) 92 to 95 weightpercent polyvinyl chloride; (b) 0.5 to 1.0 weight percent heatstabilizer; (c) 0.5 to 1.0 weight percent calcium stearate; (d) 0.9 to1.4 weight percent paraffin wax; (e) 0.05 to 0.2 weight percent oxidizedpolyethylene wax; (f) 1.0 to 2.0 weight percent titanium dioxide; (g)0.5 to 1.0 weight percent processing aid; (h) 0.1 to 1.9 weight percentof calcium carbonate; and (i) optionally, up to 2 weight percent ofpigment, based upon total weight of the pipe composition.
 15. A pipeprepared from the pipe composition of claim
 1. 16. The pipe according toclaim 15, wherein the pipe is a water pipe having a burst strength of atleast 200 psi as determined by ASTM D1785 in accordance with ASTM D1599(Procedure B).
 17. The pipe according to claim 15, wherein the pipe is agravity drain pipe, a sanitary pipe, a utility conduit, a water pipe, asewer pipe, a pressurized pipe, a pipe inserted via horizontaldirectional drilling, a pipe used in slip lining, a pipe used in a pipebursting application, a pipe used in guided boring, a pipe used indirect bury applications or any combination thereof.
 18. A pipe preparedfrom the pipe composition of claim
 14. 19. The pipe according to claim15, wherein the pipe has a diameter of from 4 inches (10 cm) to 60inches (153 cm).
 20. The pipe according to claim 15, wherein the pipehas a wall thickness of from 0.05 inches (0.125 cm) to 3 inches (7.6cm).
 21. The pipe according to claim 18, wherein the pipe is a waterpipe having a burst strength of at least 200 psi as determined by ASTMD1785 in accordance with ASTM D1599 (Procedure B).
 22. The pipeaccording to claim 18, wherein the pipe is a gravity drain pipe, asanitary pipe, a utility conduit, a water pipe, a sewer pipe, apressurized pipe, a pipe inserted via horizontal directional drilling, apipe used in slip lining, a pipe used in a pipe bursting application, apipe used in guided boring, a pipe used in direct bury applications orany combination thereof.
 23. A butt fused joint area between a firstpipe and a second pipe, the butt fused joint area being prepared fromthe composition of claim
 1. 24. A pipe system comprising a first pipe, asecond pipe and a fusion joint therebetween, wherein at least the fusionjoint is prepared from the pipe composition of claim
 1. 25. A pipesystem comprising a first pipe having a terminal edge, a second pipehaving a terminal edge, the terminal edge of the first pipe and theterminal edge of the second pipe being butt fused to form a butt fusedjoint such that an interior sidewall of the first pipe is free ofoverlap with an exterior sidewall of the second pipe and an interiorsidewall of the second pipe is free of overlap with an exterior sidewallof the first pipe, wherein at least the butt fused joint is preparedfrom the pipe composition of claim
 1. 26. A butt fused joint areabetween a first pipe and a second pipe, the butt fused joint area beingprepared from the composition of claim
 14. 27. A pipe system comprisinga first pipe, a second pipe and a fusion joint therebetween, wherein atleast the fusion joint is prepared from the pipe composition of claim14.
 28. A pipe system comprising a first pipe having a terminal edge, asecond pipe having a terminal edge, the terminal edge of the first pipeand the terminal edge of the second pipe being butt fused to form a buttfused joint such that an interior sidewall of the first pipe is free ofoverlap with an exterior sidewall of the second pipe and an interiorsidewall of the second pipe is free of overlap with an exterior sidewallof the first pipe, wherein at least the butt fused joint is preparedfrom the pipe composition of claim 14.